From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wright Subject: Re: WARNING: at drivers/iommu/dmar.c:484 warn_invalid_dmar with Intel Motherboard Date: Tue, 9 Jul 2013 17:05:11 -0700 Message-ID: <20130710000511.GC2676@sequoia2.sous-sol.org> References: <20130709202406.GA11867@roeck-us.net> <20130709223106.GA16429@roeck-us.net> <20130709232252.GB2676@sequoia2.sous-sol.org> <20130709234331.GA10833@roeck-us.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20130709234331.GA10833-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Guenter Roeck Cc: Chris Wright , Bjorn Helgaas , "open list:INTEL IOMMU (VT-d)" , David Woodhouse , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: iommu@lists.linux-foundation.org * Guenter Roeck (linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org) wrote: > On Tue, Jul 09, 2013 at 04:22:52PM -0700, Chris Wright wrote: > > * Guenter Roeck (linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org) wrote: > > > On Tue, Jul 09, 2013 at 03:05:39PM -0600, Bjorn Helgaas wrote: > > > > [+cc Joerg, David, iommu list] > > > > > > > > On Tue, Jul 9, 2013 at 2:24 PM, Guenter Roeck wrote: > > > > > I started seeing this problem after updating the BIOS trying fix another issue, > > > > > though I may have missed it earlier. > > > > > > > > > > I understand this is a BIOS bug. Would be great if someone can pass this on > > > > > to Intel BIOS engineers. > > > > > > > > Maybe. It'd be nice if Linux handled it better, though. > > > > > > > If anyone has an idea how to do that, I'll be happy to write a patch. > > > > I'm not sure there's much you can do. The BIOS is saying there's a DMAR > > unit, and then saying the registers are at addr 0x0. The kernel is > > simply warning you about the invalid DMAR table entry. > > > > One thing I've seen is the BIOS zeroing the base register address when > > VT-d is disabled in BIOS. So, Guenter, a "fix" may be simply enabling > > VT-d in the BIOS. > > Ah, yes, I think I may have that disabled. I'll check it tonight. > > Does that really warrant a traceback, or would a warning message be more > appropriate (possibly telling the user to enable VT-d) ? Bottom line, the BIOS is providing what we're seeing as invalid tables. If it's a BIOS attempt to disable VT-d is hard to glean from invalid tables, and not all BIOS give interface to enable/disable VT-d. It is a warning message, BTW. Guess I'd be inclined to leave as it is. thanks, -chris